Silver halide emulsions capable of being chemically or photo developed



United States Patent Int. Cl. G03c 1/28 US. Cl. 96-408 16 Claims ABSTRACT OF THE DISCLOSURE A photographic silver halide emulsion containing sil ver halide grains formed in the presence of tetravalent metal ions, said silver halide system having a halogen acceptor contiguous to said tetravalent metal-containing silver halide grains. In a preferred embodiment the silver halide is precipitated in acidic media. The emulsions of this invention yield good print-out emulsions which can be chemically developed to a high contrast with several types of developing solutions.

This invention relates to radiation-sensitive silver halide materials. In one aspect this invention relates to light sensitive silver halide materials which form stable, visible images either by means of conventional chemical development after exposure (i.e. developing-out system), or directly by exposure to light (i.e. print-out system). In another aspect this invention relates to a print-out emulsion which can be chemically developed to a useful contrast with several types of developing solutions.

With conventional developing-out photographic systems, as the name implies, the exposed material is chemically developed, fixed and washed. While this type of material yields a stable visible image, and has a high sensitivity, it exhibits a low propensity for the formation of print-out images.

Generally, print-out materials cannot be chemically developed to yield stable, visible images. Direct-print materials have been recently designed which do not require a chemical development step and which are of considerably higher speed than conventional print-out materials. Materials of this latter type can be chemically processed under special conditions to yield stable images but are not chemically developable with ordinary developers since the components therein tend to produce high fogv levels.

It has thus far been necessary, therefore, to prepare separate photographic silver halide emulsions for use as either a developing-out material or a printout material requiring the user to stock one or more of each of these materials depending on his requirements. Moreover, even the recently designed print-out materials which are chemically developable required the user to stock specific developers for the respective material.

It is therefore an object of this invention to provide novel radiation-sensitive silver halide systems that can be used to prepare visible images by exposure to light.

It is another object of this invention to provide novel radiation-sensitive silver halide systems that can be chemically developed in several different types of chemical developing solutions.

It is still another object of this invention to provide novel radiation-sensitive silver halide systems that can be utilized as either developing-out materials or print-out materials.

It is also an object of this invention to provide novel silver halide emulsions useful for preparing photographic proofs.

Patented Sept. 29, 1970 ice These and other objects of the invention are accomplished with a radiation-sensitive silver halide system containing unfogged silver halide grains having occluded therein tetravalent metal ions, and such silver halide system having contiguous to the tetravalent metal-containing silver halide grains a halogen acceptor.

In accordance with the invention, tetravalent metal ions are used in the precipitation or formation of the silver halide. Silver halide crystals are formed with tetravalent ions or atoms occluded therein. Typical suitable tetravalent metal ions include those of platinum, iridium,

I osmium and the like and mixtures thereof. The tetravalent metal ion can be suitably added with the Watersoluble salt (e.g. silver nitrate) or the Water-soluble halide (e.g., sodium or potassium iodide, bromide or chloride) that are combined to precipitate photographic silver halide. Likewise, the tetravalent ions can be introduced into the silver halide precipitation vessel with a hydrophilic colloid such as gelatin. The tetravalent metal ions can be added to the system as water-soluble inorganic salts, as organo-metallic materials, as complexes, or any other form of material that results in the availability of tetravalent metal ions during the formation of the silver halide. The amount of tetravalent metal utilized can be widely varied, though at least 1X10" and more generally l 10 to 2, mole percent based on silver is used. The presence of the tetravalent metal ion in the silver halide grain can be observed analytically by successively Washing the precipitated silver halide grains with a silver halide solvent such as an organic thioether or an alkali metal thiocyanate. If the tetravalent ions are only contiguous to the surface substantially all of the ions will be observed in the analysis of the first washings while substantial amounts of tetravalent ions will be found in washing just prior to complete dissolution of the silver halide grain when the ions are occluded therein.

In preparing the silver halide used in the invention, the Water-soluble silver salt and the water-soluble halide are reacted to precipitate the silver halide preferably under acidic conditions. The pH of the silver halide precipitation is typically less than 6 and preferably less than 5. Such acids as phosphoric, trifluoracetic, hydrobromic, hydrochloric, sulfuric and nitric are typically utilized in the silver halide precipitating media to maintain acidic conditions. The silver halide grains useful in the invention generally have an average grain size of about .01 to 10 microns, and more generally about .05 to 2 microns, in diameter.

Suitable silver halides include silver chloride, silver bromide, silver bromoiodide, silver chloroiodide, and silver chlorobromoiodide. The silver halide preferably contains at least 50% bromide, less than 10% iodide and less than 50% chloride on a molar basis. Both silver halide that forms latent images predominantly on the surface of the silver halide crystal or those that form latent images predominantly inside the silver halide crystal, such as those described in Davey and Knott, US. Pat. 2,592,250 issued Apr. 8, 1952, can be used in the materials of the present invention.

Various colloids can be used as vehicles or binding agents in preparing the silver halide emulsions of this invention. Satisfactory colloids which can be used for this purpose include any of the hydrophilic colloids generaly employed in the photographic field, including, for example, gelatin, colloidal albumin, polysaccharides, cellu lose derivatives, synthetic resins such as polyvinyl com pounds, including polyvinyl alcohol derivatives, acrylamide polymers and the like. In addition to the hydrophilic colloids, the vehicle or binding agent can contain hydrophobic colloids such as dispersed polymerized vinyl compounds, particularly those which increase the dimen- 3 sional stability of photographic materials. Suitable compounds of this type include water-insoluble polymers of alkyl acrylates of methacrylates, acrylic acid, sulfoalkyl acrylates or methacrylates and the like.

In addition to silver halide emulsions, vacuum deposited photographic silver halide substantially free of conventional vehicles, binders or dispersing agents can be used in the invention. Such vacuum deposited silver halide can be utilized in accordance with the invention by incorporating the halogen acceptors in a coating or layer contiguous to the vacuum deposited light-sensitive material.

The silver halide utilized in the present instance is unfogged. Such silver halide contains no visible or developable latent image. The silver halide is sensitive to electromagnetic radiation such as electrons, light and X-ray.

A wide variety of halogen acceptors can be utilized in practicing the invention. Such materials are well known to those skilled in the photographic art and are conventionally added to print-out silver halide emulsions,

Nitrogen-containing halogen acceptors are particularly useful in the invention. Suitable nitrogen-containing halogen acceptors used in the invention can be represented by the formulas,

wherein: R, R and R can each be hydrogen atoms, alkyl radicals, aryl radicals, including substituted alkyl and aryl radicals, or acyl radicals (e.g.,

wherein R is a hydrogen atom, an alkyl radical or an aryl radical); R can be a nitrogen-containing radical such as an amino radical or a thiorcarbamyl radical, including substituted amino and thiocarbamyl radicals; and D represents the necessary atoms to complete a heterocyclic nucleus generally having 5 or 6 atoms including at least two nitrogen atoms and at least one divalent radical having the formula,

wherein X can be a sulfur atom, an oxygen atom, a selenium atom or an imino radical (:NH). When a nitrogen atom is included in D or R and such nitrogen atom is attached directly to the nitrogen atoms of the above formulas, at least one hydrogen atom is attached to at least one of such nitrogen atoms of the halogen acceptor. The amino radical for substituent R can be represented by the formula,

wherein R and R can each typically be such substituents as hydrogen atoms, alkyl radicals, aryl radicals or acyl radicals as described above for R and R This thiocarbamyl radical for substituent R can be represented by the formula,

wherein R and R can be the same substituents as R and R or amino radicals.

4 Particularly useful nitrogen-containing halogen acceptors used in the invention can be further represented by the following subgeneric formulas:

wherein: R R R R R R R R R and R can each be hydrogen atoms, alkyl radicals, aryl radicals or acyl radicals as described above for R and R E can be a sulfur atom, an oxygen atom, a selenium atom or an imino radical; and Q and Z can be the necessary atoms to complete a heterocyclic nucleus generally having 5 or 6 members. Q and Z typically are the necessary atoms to complete such moieties as a triazole-thiol, a mercaptoimidazole, an imidazolidinethione, a triazinethiol, a thiobarbituric acid, a thiouracil, a urazole including a thiourazole and the like heterocyclic moieties.

With respect to the above formulas of nitrogen-containing halogen acceptors: the aryl radical substituents are those of the naphthyl and phenyl series, and include such common substituents as alkyl groups, halogen atoms, acyl radicals and the like; the alkyl radical substituents typically can contain 1 to 20 carbon atoms and more generally 1 to 8 carbon atoms, and can be substituted with such radicals as aryl radicals, halogen atoms, acyl radicals and the like.

Typical halogen acceptors of the thiourea type represented by Formula A and Formula B are disclosed in Kitze, US. Pat. 3,241,971, issued Mar. 23, 1966; and in copending Fix application, U.S. Ser. No. 338,605, filed I an. 20, 1964. Typical halogen acceptors of the hydrazine type represented by Formula C are disclosed in Ives, US. Pat. 2,588,982, issued Mar. 11, 1952. Typical halogen acceptors of the type represented by Formula D are the urazole and thiourazole halogen acceptors disclosed in Bacon and Illingsworth application, U.S. Ser. No. 406, 186 filed Oct. 23, 1964.

Examples of specific nitrogen-containing halogen acceptors that are useful in the invention are set out below.

1,3-dimethyl-2-imidazolidinethione 2-imidazolidinethione 1-phenyl-S-mercaptotetrazole Thiosemicarbazide Tetramethylthiourea p-Dimethylaminobenzaldehyde-thiosemicarbazone l-isopentyl-Z-thiourea 1-(2-diethylaminoethyl)-1,2,5,6-tetrahydro-1,3,5-triazine-4-thiol 1,2-bis-(1,2,5,6-tetrahydro-1,3,5-triazine-4-thiol) ethane 1-phenyl-2-thiourea 1,3-diphenyl-2-thiourea 4-thiobarbituric acid 2-thiouracil 1-acetyl-2-thi0urea 1,3-dibenzyl-2-thiourea 1, l-diphenyl-Z-thiourea l-ethyl- 1- a-naphthyl) -2-thiourea 2-mercaptoimidazole 5-selenourazole Hydrazine Phenylhydrazine hydrochloride 2,5-dichlorophenyl hydrazine 1-phenyl-2-imidazolidinethione 4,5-diphenyl-4-imidazolidine-2-thione 1-methyl-Z-mercaptoimidazole 1-n-butyl-1,2,5,6-tetrahydro- 1,3 ,5 -triazine-4-thiol p-Toluene sulfonyl hydrazine Hexylhydrazine Thiourea 1-methyl-2-imidazolidinethione D-mannose thiosemicarbazone Morpholino-Z-propane thiosemicarbazone D-galactose thiosemicarbazone Urazole 3-thiourazole 3,5-dithioura2ole 3,5-dithiourazole hydrazine salt 4-aminourazole hydrazine salt 3,5-dithiourazole hydrazine salt Urazole sodium salt 4-(1-naphthyl) urazole 4-ethylurazole l-phenylurazole 4-phenylurazole l-butylurazole l-octylurazole 4-butyl-3,S-dithiourazole 1,4-diphenylurazole 1,4-dibutylurazole 1,4-dibutyl-3,S-dithiourazole l,4-diphenyl-3,S-dithiourazole 1-ethyl-4-phenylurazole 1-ethyl-4-phenyl-3,S-dithiourazole 3-thio-5-iminourazole p-Tolylhydrazine hydrochloride a-Naphthylhydrazine u-Benzyl-a-phenylhydrazine Such ufeas, which include thioureas, urazoles, etc., as well as cyclic forms thereof, are merely illustrative halogen acceptors.

Other typical halogen acceptors that can be used in the invention include aromatic mercaptans such as thiosalicylic acid; hydroquinones such as hydroquinone, chlorohydroquinone, gentisic acid and t-butylhydroquinone; catechols such as phenyl catechol and t-butylcatechol; paminophenols such as N-methyl-p-aminophenol sulfate; 3-pyrazolidones such as 1-phenyl-3-pyrazolidone, 4-methyl-1-phenyl-3-pyrazolidone and l-phenyl-4,4-dimethyl-3- pyrazolidone; phenyl'enediamines; nitriles; phenols; glycine; sodium sulfite; alkaline materials such as borax, alkali metal hydroxide, etc.; and the like halogen acceptors well known to those skilled in the art.

The concentration of halogen acceptor utilized in the emulsions of the invention can be widely varied in accordance with usual practice. Generally, about .01 to 100 mole percent, and usually about .1 to mole percent, based on the silver halide in the emulsion is utilized.

The halogen acceptors are utilized contiguous to the silver halide in the present photographic system. Such halogen acceptors can be incorporated in the same photographic layer as the silver halide such as in the same emulsion layer, or in a layer adjacent to the silver halide.

The photographic silver halide system of the invention can comprise layers coated on a wide variety of supports in accordance with usual practice. Typical suitable supports include paper, polyethylene-coated paper, polypropylene-coated paper, cellulose acetate film, polyvinyl acetal film, polystyrene film, polyester films such as polyethylene terephthalate, polycarbonate film, polyimide film, and related films of resinous materials, as well as glass, metals and others.

The unexpected characteristics exhibited by my photographic silver halide system lends itself very readily to the formation of photographic proofs. When a silver halide emulsion prepared as described herein is coated with a halogen acceptor, the print-out image is unstable to further over-all exposure. However, if the halogen acceptor is removed by washing or by treatment with an oxidizing agent such as bromine water, acidic permanganate, sodium hypochlorite, N-bromosuccinimide, etc. after imagewise print-out exposure, a highly stable record is obtained. Alternatively, any method of imagewise halogen acceptor formation in the element followed by overall light exposure also gives a stable record if the silver halide emulsion layer was coated without a halogen acceptor. In either case, image fading does not occur with continued exposure.

The extremely low photographic sensitivity in the absence of a halogen acceptor, coupled with the high susceptibility to print-out in the presence of a halogen acceptor were quite surprising. Moreover, the high D and good contrast when chemically developed in several types of chemical developers were quite unexpected, especially since most prior print-out emulsions required specific developers to obtain good image properties.

Photographic elements having layers of the emulsions of this invention can be heated to elevated temperature following an initial light exposure to stabilize the image or repress printing out of unexposed or non-image areas. Elevated temperatures approaching the carbonization temperature of the support can be used in the heating process. Heat resistant supports such as polyesters, polyimides, polycarbonates and the like having high heat distortion temperatures are especially useful when a heating step is used in the image formation process.

The invention can be further illustrated by the following examples, although it will be understood that the examples are included merely for purposes of illustration and are not intended to limit the scope of the invention unless otherwise indicated.

EXAMPLE 1 A radiation-sensitive gelatino silver chlorobromide (5 mole percent chloride and mole percent bromide) photographic emulsion is prepared by slowly adding simultaneously an aqueous solution of silver nitrate and an aqueous solution of alkali metal halides to an agitated aqueous gelatin solution at 35 C. at a pH of about 2.0 adjusted with nitric acid. This emulsion is used as a control. A second emulsion is prepared in a similar manner but differing in that the aqueous gelatin solution contains 25 mg. of H PtCl per mole of silver. Each of the emulsions is then split into two portions. One portion is coated on a photographic paper with no further addenda. The other portion of the respective emulsion is treated with 5.0 mole percent of the halogen acceptor, dithiourazole hydrazine salt, based on the silver, before coating on the support. Samples of each of these coatings were given an exposure of approximately 12,500 foot-candle-minutes to a cool white fluorescent illumination. The reflection densities obtained, as read through a Wratten No. 15 filter were as follows:

Feature Halogen acceptor Density Control No 0. 04

Control 0. 96

Control plus HzPtCla. 0. 02

Control plus H2PliC16 1. 27

EXAMPLE 2 Feature MgJAg mole Halogen acceptor Density Control 0. 0t 0. 96

Control plus HzPtCle 5 0.02 Control plus H2PtClfl 5 1. 03 Control plus HzPtClt... 25 0. 02 Control plus HzPtCla 25 1. 27 Control plus H2PtClu. 75 0. 03 Control plus HZPtCls.-- 75 1. 24

7 EXAMPLE 3 Photographic emulsions are prepared in the manner described in Example 1 except K lrCl is added in place of the platinum compound. The samples are tested accord- Photographic emulsions are prepared by the procedure of Example 1 using K OsCl in place of the tetravalent platinum compound. The samples are tested according to Example 1 and give the following results:

Feature MgJAg mole Halogen acceptor Density KzOSCle 10 No 02 K2OsClu. 10 Yes 1.06

K2OSCl0... 50 N 02 KzOsCls 50 Yes 1. 13

EXAMPLE The emulsions of this invention can be chemically developed in various conventional developing solutions.

Gelatino silver chlorobromide (5 mole percent chloride, 95 mole percent bromide) photographic emulsions are prepared by adding simultaneously an aqueous solution of silver nitrate and an aqueous solution of alkali metal halides to an agitated aqueous gelatin solution containing various percentages of the tetravalent metal salt compounds listed in the table below. The emulsion is washed and 5 grams per mole of silver of the halogen acceptor, dithiourazole hydrazine salt, is added to the emulsion. The emulsion is coated on a paper support at a coverage of approximately 100 mg. of silver and 220 mg. of gelatin/ ft. Samples of the emulsion are exposed under identical conditions and comparative samples are developed for 90 seconds in Kodak D-72 Developer 1:1 (a elon-hydroquinone type developer) and for 4 minutes in Kodak D- 85 Developer (a paraformaldehyde-hydroquinone lith developer) respectively. The following results are ob- Similar results are obtained when a metol-hydroquinone developer, a paraphenylenediamine glycine developer, and a paraaminophenol hydrochloride developer are used to develop similar emulsions.

The invention has been described with reference to certain embodiments thereof for purposes of comparison of the compounds of the invention, but it will be understood that variations and modifications of the invention can be made within the scope of the following claims.

I claim:

1. A radiation-sensitive silver halide emulsion containing silver halide grains having tetravalent metal ions occluded therein, said emulsion comprising at least .01 mole percent, based on silver, of a halogen acceptor compound other than gelatin contiguous to said silver halide grains.

2. A silver halide emulsion according to claim 1 wherein said silver halide grains are formed in the presence of tetravalent metal ions in an acidic medium.

3. A silver halide emulsion according to claim 2 wherein said tetravalent metal ions are osmium, platinum or iridium ions or mixtures thereof.

4. A silver halide emulsion according to claim 1 Wherein said halogen acceptor is a urazole.

5. A silver halide emulsion according to claim 1 wherein said emulsion comprises said halogen acceptor compound in addition to a difierent material which is a primary binder vehicle for said emulsion.

6. An emulsion according to claim 1 wherein said silver halide is a silver chlorobromide.

7. An emulsion according to claim 1 wherein said halogen acceptor is a thiourea compound.

8. An emulsion according to claim 1 wherein said occluded metal ions are platinum ions.

9. An emulsion according to claim 1 wherein said occluded metal ions are osmium ions.

10. An emulsion according to claim 1 wherein said occluded metal ions are iridium ions.

11. A radiation-sensitive silver halide system containing silver halide grains formed in the presence of tetravalent iridium, osmium or platinum ions in an acidic medium, said system comprising at least .01 mole percent, based on silver, of a direct-print halogen acceptor contiguous to said silver halide grains.

12. A radiation-sensitive silver halide system according to claim 11 wherein said direct-print halogen acceptor is a nitrogen-containing halogen acceptor.

13. A radiation-sensitive silver halide system according to claim 11 wherein the halide of said silver halide is less than 10% iodide.

14. A radiation-sensitive system according to claim 11 wherein said tetravalent metal ions are present during the formation of said silver halide grains at a concentration of at least 10* mole percent, based on silver.

15. A radiation-sensitive silver halide system containing silver halide grains having tetravalent metal ions occluded therein, said silver halide system comprising gelatin and at least .01 mole percent, based on silver, of one other compound which is a halogen acceptor.

16. A radiation-sensitive system according to claim 15 wherein the halide of said silved halide is predominantly bromide.

References Cited UNITED STATES PATENTS 2,717,833 9/1955 Wark 96-108 3,123,474 3/1964 Byrne 96-94 3,367,778 2/1968 Berriman 96-108 3,418,122 12/1968 Colt 96108 1. TRAVIS BROWN, Primary Examiner US. Cl. X.R. 9694 

